Diving Deep for a Living Fossil

For 33 years, Peter A. Rona has pursued an ancient, elusive animal, repeatedly plunging down more than two miles to the muddy seabed of the North Atlantic to search out, and if possible, pry loose his quarry.

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DOWN UNDER
The submersible Alvin exploring the Mid-Atlantic, in the movie "Volcanoes of the Deep Sea," featuring Peter A. Rona and Adolf Seilacher's hunt for an organism a bit larger than a poker chip that created the fossil Paleodictyon nodosum. The search for a living specimen continues. More Photos >

Like Ahab, he has failed time and again. Despite access to the world’s best equipment for deep exploration, he has always come back empty-handed, the creature eluding his grip.

They have gathered enough evidence to prove that his scientific prey — an organism a bit larger than a poker chip — represents one of the world’s oldest living fossils, perhaps
the
oldest. The ancestors of the creature, Paleodictyon nodosum, go back to the dawn of complex life. And the creature itself, known from fossils, was once thought to have gone extinct some 50 million years ago.

Has the long pursuit frustrated him? “No,” Dr. Rona replied as he displayed traces of the animal in sedimentary rocks some 50 million years old. “It’s science. It’s detective work. It’s about racking up one clue after another.”

Still, in an interview at Rutgers, Dr. Rona said he looked forward to eventually capturing one of the creatures alive. “I think it’s likely,” he said, “if we can do the dives.” Dr. Rona, an authority on the deep sea, likes nothing better than to cram himself into a tiny submersible and fall into the abyss.

It takes more than two hours to descend to the creature’s abode, which lies more than two miles down. The environmental stability of that world — including its crushing pressures and icy darkness — means that some of its most famous inhabitants have survived for eons as evolutionary throwbacks, their bodies undergoing little change. For instance, sea lilies, marine animals with feathery arms, date back more than 400 million years.

Dr. Rona has found that P. nodosum thrives in restricted areas of Atlantic seabed. Its only visible feature consists of tiny holes arranged in six-sided patterns that look curiously like the hearts of Chinese checkers boards. He has photographed thousands of the hexagons and found that large ones have 200 or 300 holes.

Dr. Rona’s inability to catch the creature itself means that even though scientists have given it the fossil’s name, they still vigorously debate what it is. The main question is whether the hexagonal patterns are burrows or body parts, vacant residences or animal remains.

Other deep sea sleuths who share Dr. Rona’s fascination with P. nodosum can be found at Yale and the
Woods Hole Oceanographic Institution
on Cape Cod, as well as institutions in France, Canada and the United Kingdom.

“He’s got the drive of curiosity,” said Adolf Seilacher, a paleontologist at Yale and co-author of the new paper who first contacted Dr. Rona three decades ago to discuss the creature. “Real scientists, naturalists, are extremely curious.”

Dr. Seilacher added that P. nodosum was a most unusual animal, especially because the many holes at the surface of its abode link up below in a labyrinth of subsurface tunnels.

“It’s not just any fossil but a demonstration of a very complex way of life,” he said in an interview. “It’s a building plan, a behavior that makes this animal erect this gallery system. It’s a lifestyle that is very, very old.”

Dr. Seilacher said the earliest forms of Paleodictyon dated to the explosion of complex life in the Cambrian period some 500 million years ago. The animals began existence in shallow waters, he added, and gradually expanded into the dark habitats of the deep sea.

Dr. Rona became fascinated by the abyss in a roundabout way. His first love was rocks and mountains. In 1957, he received a master’s degree in geology from Yale and went to work for Standard Oil, exploring the American Southwest for promising sites.

But in 1958, while visiting his family in Manhattan over the Christmas holidays, he came upon groups of oceanographers and research ships, their vessels moored to West Side piers. The famous scientists, in New York for a meeting, spoke of a vast new world.

By the early 1970s, armed with a doctorate in marine geology and geophysics from Yale, Dr. Rona was exploring the deep Atlantic for the National Oceanographic and Atmospheric Administration. He used dredges, cameras and echo sounders that mapped the seabed.